Emulsion dewaxing of mineral oils accompanied by intensive agitation



N L e uw E mv Rwm omm om mm J F B Dec. 1, 1959 2,915,449

EMULSION DEWAXING OF MINERAL OILS ACCOMPANIED INVENTORS:

JOHANNIS DOORN United States Patent EMULSION DEWAXING 0F MINERAL OILS AC- COMPANIED BY INTENSIVE AGITATION Johannes Doom, Haarlem, and Hendrik Mondria, Willy de Rijk, and Willem Pieter Hendal, Amsterdam-Noam, Netherlands, assignors to She]! Development Company, New York, N.Y., a corporation of Delaware Application November 7, 1956, Serial No. 620,919

Claims priority, application Netherlands November 30, 1955 6 Claims. (Cl. 208-29) such circumstances that the wax passes into this auxiliary liquid. The oil phase is separated from the resulting wax-containing auxiliary liquid, and the wax is then recovered from the auxiliary liquid phase. Separation of the wax from the auxiliary liquid is generally accomplished by removing as much of the auxiliary liquid as possible by filtration. The wax is usually removed from the remaining auxiliary liquid by heating the mixture -to a temperature (about 70 C.) at which the wax liquefies. Two immiscible liquid phases, which can be readily separated, as by decanting, are formed.

It has also been found that with the use of the above processes, when involving certain oils containing paraflin wax, particularly certain Indonesian paraffinic petroleum .distillates, operating difliculties arise. For example, an emulsion prepared of a solution of Pladju petroleum distillate in 1,2-dichloroethane with an aqueous phase is allowed to stand for a long period, it is found that only a part of a paraflin wax which has passed into the upper aqueous phase rises, while a considerable amount of paraflin wax collects on the liquid-liquid interface, thus .rendering the separation of the two phases difficult and incomplete.

It is an object of the present invention to provide an improved method of dewaxing mineral oils. Another object of the present invention is to provide an improved method of dewaxing mineral oils according to the aboveoutlined procedure wherein a substantial improvement in the separation of wax from oil is obtained. Other objects and advantages will become apparent from the following detailed description.

Now, in accordance with the present invention, it has been found that in a method of dewaxing waxy mineral oils wherein the waxy oil, preferably in admixture with a suitable dewaxing solvent, is contacted with a substantial proportion of a substantially polar auxiliary liquid which is substantially immiscible therewith, and a minor :amount of a suitable surface-active agent at dewaxing temperatures and under conditions that solid wax is preferentially wetted by the auxiliary liquid and thereby is transferred thereto, and the oil phase is then separated from the resulting wax-containing auxiliary liquid phase, the foregoing objects can be achieved by subjecting the waxy oil, at least subsequent to precipitation of wax therefrom and prior to contacting with the main body of the auxiliary liquid, to intense agitation of a degree sufiicient to increase the rate of transfer of solid wax from the oil phase into the subsequently added major proportion of the auxiliary liquid phase and also to substantially reduce the proportion of contaminating oil in the separated liquid-wax phase.

The term intense agitation is not capable of exact description due to the variety of methods available for effecting such agitation. The principal types of agitation found to be most satisfactory for this purpose comprise high speed stirring, centrifugal mixing or the use of vibration with frequencies of 5000-50,000 cycles per second. High speed mixing may be obtained by both simple paddle stirrers rotating at high speeds (2,000- 10,000 rpm.) and similar or equivalent speeds of propeller and centrifugal mixers. Vibration with the above-recited range of frequencies may be applied to the waxy oil phase by means of any device for producing such vibrations.

An apparatus in which the oil phase containing paraffin wax can be conveniently subjected to the efiect of vibrations with a frequency of 5,000 to 50,000 cycles per second is shown in the accompanying figure. A supply line 2 for gas or liquid is arranged in one of the openings in a housing 1. This line carries a flange or plate 3 at the end inside the housing. At a short distance from and parallel to this flange or plate is provided a diaphragm 4 which closes an opening of the housing 1 and is pressed on to the housing by a pressing-on ring 5 provided with one or more radial openings 6. As a result of the flow of gas (e.g. air) or liquid through the narrow opening between flange 3 and diaphragm 4, an attractive force is exerted on the latter. The diaphragm thus shuts oil the gas or liquid stream, springs back again, is again attracted to the flange, etc. The required frequency and intensity of the vibrations thus produced may be adjusted by regulating the velocity of the gas or liquid stream and by a correct choice of diaphragm. The oil phase is contacted via the central opening of the ring 5 with the side of the vibrating diaphragm which is turned away from the flange, and after the treatment flows away via the radial openings 6. The gas or liquid is discharged via openings 7 in the housing. Reservoir room temperature.

10 contains the main body of the wax-oil mixture to be subjected to vibration. The mixture, having been so treated, passes through opening 6 to a receiving space 8 and is removed through outlet 9.

) It may occasionally be of advantage to quench the oil phase instead of slowing chilling .it to the dewaxing temperature. This can be carried out, for example, by heating the oil to be dewaxed, to which a small quantity vof solvent may be added, to above the cloud point of the oil phase. The phase thus obtained is finely distributed in a quantity of solvent which has been sufficiently chilled for all or practically all paraflin wax to crystallize out instantly. This process may be suitably used on petroleum fractions containing high boiling paratfin wax which can be removed from the oil even at The oil containing paraffin wax, to which approximately 525% of solvent has been added, is then heated to 60-8S C., for example, and this phase is then mixed, While stirring, with solvent having a temperature of 0-5 C. The oil is then dewaxed in the manner already described. This process can, however, also be successfully applied at lower dewaxing temperatures than room temperature.

The separation of the paraffin wax from the oil phase can be improved by adding to the oil phase, even before it has cooled, a quantity of the auxiliary phase, e.g. 520% by weight, and preferably approximately 10% by weight, calculated on the oil phase. The surface active agentmay then adhere to the resultant paraffin wax crystals even while the oil phase is being cooled and whirled. On filtering the auxiliary phase, which contains paraffin wax and is obtained during dewaxing and I melting and decanting, the paraffin wax filter cake which still contains auxiliary phase, the quantity of the auxiliary phase so obtained on this decanting may be advantageously used for adding to the oil phase before the latter is chilled.

If it is desired to improve still further the separation of the paraffin wax and the oil, after the separation of the oil phase, which usually contains solvent, the auxiliary phase, containing paraffin wax, may be washed with a quantity of solvent. For this preferably the same solvent is used as that with which the oil phase is mixed. The solvent dissolves the oil which has remained emulsified in the auxiliary phase. It is also possible first to separate the whole auxiliary phase or a part thereof from the parafiin wax by decanting or filtering, and then to wash the parafiin wax with water. In both cases, after the washing, the solvent, which usually does not contain more than 0.5% by weight of oil, may be directly used for mixing with a fresh quantity of oil containing paraffin wax.

An organic solvent is generally employed in the abovedescribed dewaxing operation. The organic solvent used should be a good dewaxing solvent, that is, it should be a good solvent for oil, but substantially a non-solvent for solid wax. Suitable dewaxing solvents include halogenated hydrocarbons such as ethylene dichloride, ethylene dibromide, chloroform, carbon tetrachloride, ethyl chloride, propyl chloride, ethyl bromide, propyl bromide, trichloroethane, tetrachloroethane, propylene chloride, trimethylene chloride, amyl bromide, tertiary amyl chloride, butyl chloride, butyl bromide, allyl bromide, beta,beta-dichlorodiethyl ether, chlorobenzene, bromobenzene, o-dichloro-benzene, tetrachloroethylene, tetrafiuoroethylene, 2-chlorophenylamine, 3 -chlorophenylamine, and l-amino-2-fluorobenzene; aliphatic and aromatic hydrocarbons such as petroleum ether, petroleum naphtha, gasoline, pentane, isopentane, hexane, heptane, octane, benzene, propylbenzene, cumene, amylbenzene, toluene, xylene, and cymene; ketones such as methyl isopropyl ketone, methyl isobutyl ketone, methyl ethyl ketone and mixtures thereof with hydrocarbons such as benzene and/or toluene; and other compounds such as nitrobenzene, furfural, aniline, toluidine, o-aminoethylbenzene, m-aminoethylbenzene, N-methylaniline, N- ethylphenylamine, p-methoxy-aniline, 1-ethoxybutane, and methylphenyl ether as Well as various mixtures there of, and with other solvents.

It is preferred that the dielectric constant of the oilsolvent phase be from about 2 to about 15, and preferably from about 3 to about 10.

The solvent is employed in the ratio of from about 3 to about parts by weight of solvent to 1 part of oil.

The auxiliary liquid employed should have a higher dielectric constant than the oil phase and should be substantially immiscible therewith. In general, the auxiliary liquid should be strongly polar in character. Water, or an aqueous liquid is, therefore, preferred. As a rule, at least 50% of the auxiliary liquid consists of water. Lower alcohols, glycol or glycerol can be used alone as the auxiliary liquid, but combinations thereof with water are generally preferred. In order to lower the freezing point of water, salts, such as NaCl or CaCl or alcohols, such as methyl or ethyl alcohol or ethylene glycol, can be added. The amount of auxiliary liquid employed should be sufficient to enable it to readily absorb the wax particle. The volume ratio of auxiliary liquid to oil phase should be at least 1:1, preferably in the range of from about 1:1 to about 3:1.

In order to effect satisfactory separation of the aqueous or other auxiliary liquid phase from the oil phase, it is necessary that the dielectric constant of the two liquid phases be adjusted so that the contact angle of the solid wax in the oil-solvent phase has a value of at least 90 and preferably at least 10. The contact angle, generally represented by the symbol [3, is the angle which the interfacial tension of the two liquid phases, represented by 7, forms with the solid wax.

On dewaxing, demixing of the oil plus solvent phase should be prevented. It has ben found, for example, that with the use of a mixture of by weight of dichloroethane and 20% by weight of benzene as solvent satisfactory results are usually obtained in this respect. The benzene may be wholly or partly replaced by toluene.

As a result of the presence of the surface-active agent emulsions may be readily formed While the auxiliary phase and oil phase are being contacted. It is, however, necessary for the separation of the paraffin wax from the oil phase and for the separation of the liquid phases from each other, that these emulsions should not be stable. The formation of stable emulsions can be prevented by adding a demulsifier which does not adversely affect the action of the surface-active agent. As demulsifiers may be mentioned divalent metals salts such as MgSO MgCl CaCI CaSO Ni(NO Zn(NO FeSO CuSO CdCl and MnSO as well as lithium and ammonium salts, organic demulsifiers such as cyclohexylamine, phenol, diphenylamine, amyl alcohol, dodecyl alcohol and cyclohexanol, which have no effect in themselves, but are active when used together with a salt such as Na SO as Well as a number of non-ionic surface-active agents such as condensation products of fatty acids and ethylene oxide, and similar compounds which are also active only when together with a salt such as Na SO The amount in which these demulsifiers are added is usually 0.00005-0.1% by weight, calculated on the auxiliary phase.

It is also necessary to prevent the auxiliary phase from freezing. This can be done by adding freezing point reducers.

Organic compounds such as alcohols, e.g. methanol, ethylene glycol and glycerol, are primarily suitable for this purpose. Since the two latter alcohols considerably increase the viscosity of the auxiliary phase, methanol is preferred.

Inorganic compounds, e.g. metal salts such as NaCl and CaCl can also be used as freezing point reducers.

It is found that when the oil phase and auxiliary phase are emulsified in such a way that an oil-in-water emulsion is formed, the paraflin wax often passes into the auxiliary phase more readily when the pH of the auxiliary phase is 7. In order to effect this, a small quantity of an alkali metal hydroxide solution or ammonium hydroxide solution is added to the auxiliary phase.

The surface-active agent which it is desired to use may be chosen relatively at will. The choice is also determined by the dewaxing process used, viz, whether it is desired to obtain an oil-in-auxiliary phase or an auxiliary phase-in-oil emulsion. For carrying out the dewaxing in practice, it is advantageous to choose a surface-active agent which is readily soluble in the auxiliary phase, since when, in this case, the auxiliary phase is recycled after use in order to dewax a fresh quantity of oil phase therewith, it is only necessary to supply a small amount of surface-active agent as only a small amount has remained behind in the oil phase.

With the use of Na-C C -2-sulfates or mixtures predominantly comprising these 2-sulfates, as surfaceactive agent, it is desirable to use 05-10% by weight of a salt of a monovalent metal or of an ammonium salt, and 05-15% by weight of an alcohol having 1-8 carbon atoms in the molecule, calculated on the auxiliary phase.

When dewaxing at low temperatures it is preferable to add one or more ammonium salts and/or ammonium hydroxide in an amount of more than 0.5% by weight, calculated on the auxiliary phase.

The invention is illustrated by the following examples.

li'xample I Specific gravity 70/4 0.8137 Boiling range C 375-480 Viscosity at 99 C cs 4.61

was dewaxed in a pilot plant both according to the process used hitherto and according to the invention.

In each experiment 33 /2 liters of 1,2-dichloroethane containing 70 gm. of isoamyl alcohol per liter, were added to 7 liters of this distillate, after which the mixture was thoroughly stirred at 70 C. On chilling to 10 C. a'suspension of solid paraffin wax in oil and solvent was obtained. Onesuspension (A) was now thoroughly stirred in a 3-stage stirrer of which the blades revolved at 2,800 r.p.m., and then emulsified in 80 liters of an aqueous phase containing 1.25 gm. of an aqueous solution of asurface-active agent mixture containing more than 70% by weight of NaC --C -2-sulfates and 28 gm. of NaCl per liter, while the other suspension (B), without first having been vigorously stirred, was emulsified in 80 liters of the same aqueous phase. The paraffin wax passed much more rapidly into the aqueous phase, and the two liquid phases could be more readily separated, in the first case than in the second. The two mixtures were then further treated in the same way. After separation of the oil-solvent phase, the paraffin wax-water suspension was washed with 33 /2 liters of 1,2-dichloroethane to which had been added 70 gm. of isoamyl alcohol per liter. After melting the washed suspension of paraffin wax and water, a parafiin wax was obtained having-an oil content of 0.5% by weight in the case of suspension (A) and an oil content of 8% by weight in the'case of suspension (B) (determined according to ASTM D-72l).

Example II The same initial material as in Example I was dewaxed at 0 C. according to the same processes as described in the said example, except that the suspension, whether or not thoroughly stirred, was emulsified in 80 liters of an aqueous phase containing per liter 1.2 gm. of sodium dodecyl benzene sulfonate, 35 gm. of

Example III A Pladju parafi'inic petroleum distillate having the following properties:

Specific gravity 70/4 0.856 Redwood I viscosity at 60 C sec 64.5 Boiling range C 340-475 was mixed with 5 parts by weight of 1,2-dichloroethane per part by weight of oil, heated to 70 C., and then cooled to +5 C. The mixture obtained was divided into two parts, one part (A) being mixed in a high speed centrifugal mixer, and then mixed with an aqueous phase, while the other part (B) was mixed with an aqueous phase without being stirred. In both cases the aqueous phase contained per liter 1 gm. of sodium benzene dodecyl sulfonate, 25 gm. of NH Cl and 250 gm. of methanol and the ratio by weight of aqueous phase to oil phase was 1.5 :l.

The results are summarized in the following table: I

Treatment A B Yield of dewaxed oil, percent by wt 65. 8 55. 0 Melting point of parafiin wax before washing with 1,2-d1- chloro-ethane, C 55. 8 50.6 Oil content of paraffin wax before washing with 1,2(11- chloro-ethane, percent by wt 3.3 26.6 Melting point of parafiin wax after washing with 1,2-d1- 56. 1 52. 8 chloro-ethane, 0 56.1 52. 8 Oil content of parafiin wax after washing with 1,2-dichloro- 56. 1

ethane, percent by wt 1. 4 19. 2

Example IV In an apparatus shown in the accompanying drawing, the initial material referred to in Example I was treated in the manner indicated in that example, except that suspension A was not stirred but passed over a diaphragm arranged as shown in the figure. The diaphragm vibrated with a frequency of 9,000 cycles per second, at'which frequency the elfect was found to he maximum. Without subsequently washing with dichloroethane, the oil content of the paraffin wax obtained from suspension A was 5.7% by weight, while the oil content of the paraffin wax obtained from suspension B was 13.5% by weight.

We claim as our invention:

1. In a method of dewaxing a waxy mineral oil, the combination of steps comprising: 1) mixing the waxy mineral oil with a substantial proportion of a dewaxing sol-vent for the mineral oil but which is substantially a non-solvent for solid wax; (2) cooling the mixture to a dewaxing temperature at which the wax solidifies, thereby forming a dispersion of solid wax particles in a liquid oil phase which is a solution of the oil and the solvent; (3) subjecting the cooled mixture to vibrations having a he quency of 5,000-S0,000 cycles per second; (4) intimately mixing the resulting dispersion of solid wax dispersed in the oil phase with a substantial proportion, at least equal in volume to the volume of the oil phase, of a substantial- 1y polar auxiliary liquid which is substantially immiscible therewith and which has a dielectric constant higher than that of the oil phase, and with a minor amount of a surface-active agent, the entire system being essentially at the dewaxing temperature, whereby two liquid phases result, an oil phase consisting essentially of mineral oil and solvent and an auxiliary liquid phase containing dissolved said surface-active agent, and correlating the dielectric constants of the two liquid phases so that the contact angle in the oil phase is at least 90, whereby the soild wax is preferentially wetted by the auxiliary liquid phase and is transferred thereto to produce a dispersion of the solid wax in the auxiliary liquid phase as the continuous phase, while the oil phase is substantially free from wax; (5) stratifying and separating the oil phase from the auxiliary liquid phase containing the dispersion of soild wax; the agitation in step (3) being suflicient to substantially increase the rate of transfer of solid wax from the oil phase into the auxiliary liquid phase and to substantially reduce the proportion of contaminating oil in the separated auxiliary liquid-wax phase.

2. A method according to claim 1, wherein the auxiliary liquid is an aqueous liquid.

3. A method according to claim 1, wherein the oil phase is quenched before vibration.

4. A method according to claim I, wherein vibration is employed during and after cooling to a dewaxing temperature.

forming a dispersion of solid wax particles in a liquid oil phase which is a solution of the oil and the solvent; (3) subjecting the cooled mixture to stirring at a stirrer speed of 2,000-l0,000 r.p.m.; (4) intimately mixing the resulting dispersion of solid wax dispersed in the oil phase with a substantial proportion, at least equal in volume to the volume of the oil phase, of a substantially polar auxiliary liquid which is substantially immiscible therewith and which has a dielectric constant higher than that of the oil phase, and with a minor amount of a surface-active agent, the entire system being essentially at the dewaxing temperature, whereby two liquid phases result, an oil phase consisting essentially of mineral oil and solvent and an auxiliary liquid phase containing dissolved said surface-active agent, and correlating the dielectric constants of the two liquid phases so that the contact angle in the oil phase is at least 90, whereby the solid wax is preferentially wetted by the auxiliary liquid phase and is transferred thereto to produce a dispersion of the solid wax in the auxiliary liquid phase as the continuous phase,

while the oil phase is substantially free from wax; (5) stratifying and separating the oil phase from the auxiliary liquid phase containing the dispersion of solid wax; the agitation in step (3) being sutficient to substantially increase the rate of transfer of solid wax from the oil phase into the auxiliary liquid phase and to substantially reduce the proportion of contaminating oil in the separated auxiliary liquid-wax phase;

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN A METHOD OF DEWAXING A WAXY MINERAL OIL, THE COMBINATION OF STEPS COMPRISING: (1) MIXING THE WAXY MINERAL OIL WITH ASUBSTANTIAL PROPORTION OF A DEWAXING SOLVENT FOR THE MINERAL OIL BUT WHICH IS SUBSTANTIALLY A NON-SOLVENT FOR SOLID WAX; (2) COOLING THE MIXTURE TO A DEWAXING TEMPERATURE AT WHICH THE WAX SOLIDIFIES, THEREBY FORMING A DISPERSION OF SOLID WAX PARTICLES IN A LIQUID OIL PHASE WHICH IS A SOLUTION OF THE OIL AND THE SOLVENT; (3) SUBJECTING THE COOLED MIXTURE TO VIBRATIONS HAVING A FREQUENCY OF 5,000-50,000 CYCLES PER SECOND; (4) INTIMATELY MIXING THE RESULTING DISPERSION OF SOLID WAX DISPERSED IN THE OIL PHASE WITH A SUBSTANTIAL PROPORTION, AT LEAST EQUAL IN VOLUME TO THE VOLUME OF THE OIL PHASE, OF A SUBSTANTIALLY POLAR AUXILIARY LIQUID WHICH IS SUBSTANTIALLY IMMISCIBLE THEREWITH AND WHICH HAS A DIELECTRIC CONSTANT HIGHER THAN THAT OF THE OIL PHASE, AND WITH A MINOR AMOUNT OF A SURFACE-ACTIVE AGENT, THE ENTIRE SYSTEM BEING ESSENTAILLY AT THE DEWAXING TEMPERATURE, WHEREBY TWO LIQUID PHASES RESULT, AN OIL PHASE CONSISTING ESSENTIALLY OF MINERAL OIL AND SOLVENT AND AN AUXIALLARY LIQUID PHASE CONTAINING DISSOLVED SAID SURFACE-ACTIVE AGENT, AND CORRELATING THE DIAELECTRIC CONSTANTS OF THE TWO LIQUID PHASES SO THAT THE CONTACT ANGLE IN THE OIL PHASE IS AT LEAST 90*, WHEREBY THE SOLIDS WAX IS PREFERENTIALLY WETTED BY THE AUXILIARY LIQUID PHASE AND IS TRANSFERRED THERETO TO PRODUCE A DISPERSION OF THE SOLID WAX IN THE AUXILIARY LIQUID PHASE AS THE CONTINUOUS PHASE, WHILE THE OIL PHASE IS SUBSTANTIALLY FREE FROM WAX; (5) STRATIFYING AND SEPARATING THE OIL PHASE FROM THE AUXILIARY LIQUID PHASE CONTAINING THE DISPERSION OF SOLID WAX; THE AGITATION IN STEP (3) BEING SUFFICIENT TO SUBSTANTIALLY INCREASE THE RATE OF TRANSFER OF SOLID WAX FROM THE OIL PHASE INTO THE AUXIALLARY LIQUID PHASE AND TO SUBSTANTIALLY REDUCE THE PROPORTION OF CONTAMINATING OIL IN THE SEPARATED AUXIALLARY LIQUID-WAX PHASE. 